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Glossary

Interference with the rotator cuff footprint

The entry point for a bent nail may go through the bony attachment of the rotator cuff. This bony defect in the footprint cannot be reconstructed later.

The entry point for a straight nail lies under the rotator cuff so the nail is inserted through the rotator cuff. This requires an incision, which should be made in the line of the tendon fibers which can then be closed effectively by a side to side suture.

Fixation in osteoporotic bone, fifth anchoring point

Due to the bone density in osteopenic bone straight nails provide a better fixation in the proximal humerus in the region of their entry point. Bent nails run through the greater tuberosity which has a lower bone density compared to the superior humeral head.

Interference with fracture lines

In proximal humeral fractures which consist of a fracture of the greater tuberosity the trajectory of bent nails often passes through the fracture line between the greater tuberosity and the humeral head whereas straight nails penetrate the humeral head medial to the fracture line.

Correct nail entry point

It might be difficult or even not possible to access the correct entry point if the humeral head is displaced severely into a varus position. Therefore, it is strongly recommended to expose the entry point by manipulating the humeral head. K-wire “joy-sticks” (as illustrated) or sutures through the rotator cuff insertions can be used to achieve this.

Reduction of the metaphyseal fracture component

Protection of axillary nerve

The main structure at risk is the axillary nerve. The axillary nerve should be protected by limiting the incision to less than 5 cm distal to the acromial edge, by palpating the nerve, and by avoiding maneuvers that stretch the nerve during reduction and fixation.

In addition, any suspicious screw trajectory should be made to the bone with blunt dissection and checked with finger palpation if necessary.

Insert nail and reduce fracture

Insert the nail with slightly rotating movements down to the metaphyseal fracture line. Pass the fracture zone under image intensification and make sure that the nail enters the distal fragment properly.

Retrotorsion of locking device

In order to lock the nail in the correct trajectory, mount the aiming arm and swivel it approximately 25° anteriorly in order to follow the retroverted axis of the humeral head. (Due to the physiological retrotorsion of the humeral head, the axis of the humeral head is directed approximately 25° posteriorly to the condylar plane of the distal humerus.)

Mount aiming device and insert trocar combination

Mount the aiming device in the insertion handle. Confirm that the retroversion angle is correct. Make a skin incision for the aiming device, dissect the muscles bluntly down to the bone, and fully insert the trocar.

Determine length of spiral blade

Open the lateral cortex

Insert spiral blade

Attach the spiral blade to the inserter and introduce both over the guide wire.

Align the handle of the inserter parallel to the aiming arm.

The initial rotation of the T-handle of the spiral blade inserter relative to the aiming arm depends on patient anatomy. If the distance from the lateral cortex to the nail is less than 10 mm, start the inserter slightly clockwise from parallel. If the distance from the lateral cortex to the nail is more than 10 mm, start the T-handle slightly counter-clockwise from parallel.

By applying light controlled hammer blows to the connecting screw, advance the spiral blade to the desired depth. This causes the handle to rotate 90°.

Monitor the depth of the spiral blade with image intensification. If attaching sutures to the spiral blade, pause when the spiral blade is approximately 1.5 cm to 2.0 cm short of its intended position so that the suture ends can be placed through the appropriate holes in the base blade.

Insertion of additional head screw

Drill and determine length of locking screw

For distal locking, insert the two-piece trocar combination (aiming arm). Through an appropriately placed trocar, drill through both humeral cortices until the bit just breaks through the medial cortex and read the depth from the drill bit. Alternatively, a depth gauge can be used.

Insert a locking screw through the trocar. A second screw is recommended, especially in osteoporotic bone.

Pearl: Make one incision large enough to allow palpation of the axillary nerve.